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Acta Oceanologica Sinica

, Volume 38, Issue 11, pp 1–10 | Cite as

Origin and formation of the Ryukyu Current revealed by HYCOM reanalysis

  • Min Wang
  • Zhaojun Liu
  • Xiaohua ZhuEmail author
  • Xiaomei Yan
  • Zhongzhe Zhang
  • Ruixiang Zhao
Article
  • 11 Downloads

Abstract

The origin of the Ryukyu Current (RC) and the formation of its subsurface velocity core were investigated using a 23-year (1993–2015) global Hybrid Coordinate Ocean Model (HYCOM) dataset. The volume transport of the RC comes from the Kuroshio eastward branch (KEB) east of Taiwan and part of the North Pacific Subtropical Gyre (p-NPSG). From the surface to 2 000 m depth, the KEB (p-NPSG) transport contributes 41.5% (58.5%) to the mean total RC transport. The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge (sill depth: 700 m). Above 700 m, the Kuroshio can enter the East China Sea (ECS) over the Ilan Ridge, meanwhile, the blocked Kuroshio below 700 m turns to the right and flows along the Ryukyu Islands. With the RC flowing northeastward, the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge. In the surface layer, the p-NPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps (with net volume transport into ECS) between the Ryukyu Islands.

Key words

origins of Ryukyu Current subsurface velocity core volume transport Kuroshio HYCOM 

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References

  1. Andres M, Park J H, Wimbush M, et al. 2008. Study of the Kuroshio/Ryukyu Current system based on satellite-altimeter and in situ measurements. Journal of Oceanography, 64(6): 937–950, doi:  https://doi.org/10.1007/s10872-008-0077-2 CrossRefGoogle Scholar
  2. Chang Y L, Oey L Y. 2011. Interannual and seasonal variations of Kuroshio transport east of Taiwan inferred from 29 years of tide-gauge data. Geophysical Research Letters, 38(8): L08603, doi:  https://doi.org/10.1029/2011GL047062 CrossRefGoogle Scholar
  3. Cummings J A, Smedstad O M. 2013. Variational data assimilation for the global ocean. In: Park S K, Xu Liang, eds. Data Assimilation for Atmospheric, Oceanic and Hydrologic Applications (Vol. II). Berlin, Heidelberg: Springer-Verlag, 303–343CrossRefGoogle Scholar
  4. Ichikawa H, Nakamura H, Nishina A, et al. 2004. Variability of northeastward current southeast of northern Ryukyu Islands. Journal of Oceanography, 60(2): 351–363, doi:  https://doi.org/10.1023/B:JOCE.0000038341.27622.73 CrossRefGoogle Scholar
  5. Johns W E, Lee T N, Zhang Dongxiao, et al. 2001. The Kuroshio east of Taiwan: moored transport observations from the WOCE PCM-1 Array. Journal of Physical Oceanography, 31(4): 1031–1053, doi: 10.1175/1520-0485(2001)031CrossRefGoogle Scholar
  6. Kamachi M, Kuragano T, Ichikawa H, et al. 2004. Operational data assimilation system for the Kuroshio south of Japan: reanalysis and validation. Journal of Oceanography, 60(2): 303–312, doi:  https://doi.org/10.1023/B:JOCE.0000038336.87717.b7 CrossRefGoogle Scholar
  7. Metzger E J, Hurlburt H E, Xu X, et al. 2010. Simulated and observed circulation in the Indonesian seas: 1/12° global HYCOM and the INSTANT observations. Dynamics of Atmospheres and Oceans, 50(2): 275–300, doi:  https://doi.org/10.1016/j.dynatmoce.2010.04.002 CrossRefGoogle Scholar
  8. Na Hanna, Wimbush M, Park J H, et al. 2014. Observations of flow variability through the Kerama Gap between the East China Sea and the northwestern Pacific. Journal of Geophysical Research, 119(2): 689–703, doi:  https://doi.org/10.1002/2013JC008899 Google Scholar
  9. Nagano A, Ichikawa H, Miura T, et al. 2007. Current system east of the Ryukyu Islands. Journal of Geophysical Research, 112(C6): C06009, doi:  https://doi.org/10.1029/2006JC003917 CrossRefGoogle Scholar
  10. Nakamura H, Ichikawa H, Nishina A. 2007. Numerical study of the dynamics of the Ryukyu Current system. Journal of Geophysical Research, 112(C4): C04016, doi:  https://doi.org/10.1029/2006JC003595 CrossRefGoogle Scholar
  11. Nitani H. 1972. Beginning of the Kuroshio. In: Stommel H, Yoshida K, eds. Kuroshio: Its Physical Aspects. Tokyo: University of Tokyo Press, 129–163Google Scholar
  12. Saha S, Moorthi S, Pan Hualu, et al. 2010. The NCEP climate forecast system reanalysis. Bulletin of the American Meteorological Society, 91(8): 1015–1058, doi:  https://doi.org/10.1175/2010BAMS3001.1 CrossRefGoogle Scholar
  13. Thoppil P G, Metzger E J, Hurlburt H E, et al. 2016. The current system east of the Ryukyu Islands as revealed by a global ocean reanalysis. Progress in Oceanography, 141: 239–258, doi:  https://doi.org/10.1016/j.pocean.2015.12.013 CrossRefGoogle Scholar
  14. Yan Xiaomei, Zhu Xiaohua, Pang Chongguang, et al. 2016. Effects of mesoscale eddies on the volume transport and branch pattern of the Kuroshio east of Taiwan. Journal of Geophysical Research, 121(10): 7683–7700, doi:  https://doi.org/10.1002/2016JC012038 Google Scholar
  15. You S H, Yoon J H. 2004. Modeling of the Ryukyu current along the pacific side of the Ryukyu islands. Pacific Oceanography, 2: 44–51Google Scholar
  16. Yu Zhitao, Metzger E J, Thoppil P, et al. 2015. Seasonal cycle of volume transport through Kerama Gap revealed by a 20-year global HYbrid Coordinate Ocean Model reanalysis. Ocean Modelling, 96: 203–213, doi:  https://doi.org/10.1016/j.ocemod.2015.10.012 CrossRefGoogle Scholar
  17. Yuan Yaochu, Kaneko A, Su Jilan, et al. 1998. The Kuroshio east of Taiwan and in the East China Sea and the currents east of Ryukyu Islands during early summer of 1996. Journal of Oceanography, 54(3): 217–226, doi:  https://doi.org/10.1007/BF02751697 CrossRefGoogle Scholar
  18. Zhang Dongxiao, Lee T N, Johns W, et al. 2001. The Kuroshio East of Taiwan: modes of variability and relationship to interior ocean mesoscale eddies. Journal of Physical Oceanography, 31(4): 1054–1074, doi: 10.1175/1520-0485(2001)031<1054:TKEOTM>2.0.CO;2CrossRefGoogle Scholar
  19. Zhou Wenzheng, Yu Fei, Nan Feng. 2017. Water exchange through the Kerama Gap estimated with a 25-year Pacific HYbrid Coordinate Ocean Model. Chinese Journal of Oceanology and Limnology, 35(6): 1287–1302, doi:  https://doi.org/10.1007/s00343-017-6141-2 CrossRefGoogle Scholar
  20. Zhu Xiaohua, Han I S, Park J H, et al. 2003. The northeastward current southeast of Okinawa Island observed during November 2000 to August 2001. Geophysical Research Letters, 30(2): 1071, doi:  https://doi.org/10.1029/2002GL015867 Google Scholar
  21. Zhu Xiaohua, Ichikawa H, Ichikawa K, et al. 2004. Volume transport variability southeast of Okinawa Island estimated from satellite altimeter data. Journal of Oceanography, 60(6): 953–962, doi:  https://doi.org/10.1007/s10872-005-0004-8 CrossRefGoogle Scholar
  22. Zhu Xiaohua, Park J H, Kaneko I. 2005. The northeastward current southeast of the Ryukyu Islands in late fall of 2000 estimated by an inverse technique. Geophysical Research Letters, 32(5): L05608, doi:  https://doi.org/10.1029/2004GL022135 CrossRefGoogle Scholar
  23. Zhu Xiaohua, Park J H, Kaneko I. 2006. Velocity structures and transports of the Kuroshio and the Ryukyu Current during fall of 2000 estimated by an inverse technique. Journal of Oceanography, 62(4): 587–596, doi:  https://doi.org/10.1007/s10872-006-0078-y CrossRefGoogle Scholar
  24. Zhu Xiaohua, Park J H, Wimbush M, et al. 2008. Comment on “Current system east of the Ryukyu Islands” by A. Nagano et al. Journal of Geophysical Research, 113(C3): C03020, doi:  https://doi.org/10.1029/2007JC004458 CrossRefGoogle Scholar

Copyright information

© Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Min Wang
    • 1
    • 2
  • Zhaojun Liu
    • 2
  • Xiaohua Zhu
    • 1
    • 2
    Email author
  • Xiaomei Yan
    • 3
  • Zhongzhe Zhang
    • 4
  • Ruixiang Zhao
    • 2
  1. 1.School of OceanographyShanghai Jiao Tong UniversityShanghaiChina
  2. 2.State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of OceanographyMinistry of Natural ResourcesHangzhouChina
  3. 3.Key Laboratory of Ocean Circulation and Waves, Institute of OceanologyChinese Academy of SciencesQingdaoChina
  4. 4.College of Marine Science and EnvironmentDalian Ocean UniversityDalianChina

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